Hydraulic lash adjuster equipped with auxiliary check valve

ABSTRACT

An auxiliary check valve is provided in a hydraulic lash adjuster of the type wherein the plunger-to-body clearance is sealed. The auxiliary check valve is derived so that it remains open until the plunger has been moved to the limit of its travel by rotation of the engine camshaft during engine assembly. The auxiliary check valve permits fluid within the hydraulic lash adjuster high pressure chamber to be displaced to the reservoir chamber allowing the hydraulic lash adjuster to shorten from its free length to the proper installed length.

FIELD OF THE INVENTION

The present invention relates to valve trains for internal combustionengines. More particularly, the present invention relates to an improvedhydraulic lash adjustment device for use in a valve train for internalcombustion engines.

BACKGROUND OF THE INVENTION

This invention relates to hydraulic lash adjusters for internalcombustion engines and to a system comprising a hydraulic lash adjusterin combination with an auxiliary check valve therefore. Those skilled inthe art of engine valve train design recognize that hydraulic lashadjusters are variable length devices capable of automatically varyingtheir length to eliminate any gaps or “lash” within a valve trainsystem.

Upon installation into an engine valve train, hydraulic lash adjustersshorten from their free, extended length to an installed lengthconsistent with positive closure of their associated engine valves. Theinstalled length varies by engine valve location due to valve trainsystem manufacturing variations, temperature, and wear. As disclosed inU.S. Pat. Nos. 2,956,557 and 6,598,572, hydraulic lash adjustersincorporate a combination seal-check valve which closes the highpressure chamber within the hydraulic lash adjuster as necessary totransmit cam motion to an engine valve. The disclosure of U.S. Pat. No.6,598,572 differs from that of U.S. Pat. No. 2,956,557 in that theformer adds a spring which biases the combination seal-check valvenormally open.

As a practical matter, these prior art hydraulic lash adjusters aredifficult, if not impossible, to install in an engine valve train duringautomated assembly and also during manual assembly under ordinaryenvironmental conditions. During installation of these prior arthydraulic lash adjusters, an internal plunger displaces fluid from thehigh pressure chamber to the reservoir past a combination seal-checkvalve. However, viscous drag forces coincident to fluid flow cause thecombination seal-check valve to close, halting both fluid flow andplunger motion, and thereby preventing the hydraulic lash adjuster fromassuming the proper installed length. With respect to the hydraulic lashadjuster disclosed in U.S. Pat. No. 6,598,572, the viscosity andvelocity of the fluid displaced around the combination seal-check valvetends to produce viscous drag forces which exceed the leaf spring load,prematurely, thereby closing the check valve and preventing thehydraulic lash adjuster from assuming the proper and desired installedlength. The occurrence of installation difficulties of this kind is aprincipal reason why prior art hydraulic lash adjusters that incorporatea combination seal-check valve are not commonly in commercial use.

SUMMARY OF THE INVENTION

The invention comprises an improvement in hydraulic lash adjusters ofthe type described in U.S. Pat. No. 2,956,557 which incorporate acombination seal-check valve. The improvement comprises an auxiliarycheck valve system, the purpose of which is to facilitate installationof this particular type of hydraulic lash adjuster into an engine valvetrain. An overview of an engine valve train is described in U.S. Pat.No. 2,956,557 and that description is incorporated herein by reference.In accordance with the invention, the novel auxiliary check valveprovided by the invention is devised to be maintained in the open stateuntil installed in an engine valve train and the camshaft is rotatedthrough one full revolution. In the installation the first actuation ofthe valve train bottoms the plunger, thereby semi-permanently closingthe auxiliary check valve of the invention which is devised to bemaintained closed by means such that the bottoming action of the plungerassembly, fits into or over a feature on the bottom of the plungerassembly so as to permanently or semi-permanently close off the highpressure chamber until such time as the valve train requires service andthe check valve is manually reset to the open state.

To ensure proper valve train operation, hydraulic lash adjusters must,during each valve event, shorten from their operating length by anamount slightly greater than that required to ensure positive closure ofthe associated engine valves. This is especially true when starting anengine at extreme cold environmental conditions, e.g., at temperaturesof the order at about 40° C. A “valve event” herein is defined as theperiod during which cam lift is non-zero. At the end of the valve event,the hydraulic lash adjuster must automatically extend to an operatinglength consistent

The invention differs from known prior art hydraulic lash adjusterswhich comprise an external, cylindrical body within which is slideablyfitted a cylindrical plunger equipped with a check valve that limits theflow of fluid, usually engine oil, out of a “high pressure” chamberenclosed by the body and the plunger. The plunger is select fitted tothe body with a typical plunger-to-body diametrical clearance ofapproximately 5.1-5.8 μm (0.000200-0.000230 in.) to provide an annularpassageway through which a small amount of fluid may be displaced fromthe high pressure chamber during the valve event, thereby allowing thehydraulic lash adjuster to shorten from its operating length inanticipation of dimensional changes in the associated valve traincomponents due to thermal effects and wear. At the end of the valveevent, a plunger return spring concurrently extends the plunger toeliminate lash and the check valve opens to permit the passage of fluidfrom the internal reservoir to the high pressure chamber.

As noted hereinabove, the hydraulic lash adjuster of this inventionpertains to the kind described in U.S. Pat. No. 2,956,557 which differsfrom those commonly in production today in that it incorporates acombination seal-check valve in lieu of the select fit plunger-to-bodyclearance and separate check valve. In the type of hydraulic lashadjuster described in U.S. Pat. No. 2,956,557, since the plunger-to-bodyclearance is essentially sealed, instead of shortening from itsoperating length over the entire duration of the valve event, itshortens from its operating length only at the beginning of the valveevent. It does so when the plunger is moved through the distancenecessary to abut the seal against the seal gland, e.g., 0.13 mm (0.005in.). A hydraulic lash adjuster of that kind is difficult, if notimpossible, to install in an engine valve train because the plunger musttypically be depressed up to 2 mm (0.080 in.) to attain the appropriateinstalled length.

This invention accordingly has the objective of providing an improvementover prior art hydraulic lash adjusters of the type described in U.S.Pat. No. 2,956,557 and U.S. Pat. No. 6,598,572 by the addition of anauxiliary check valve which permits the plunger to be freely depressedto the limit of its travel and by this action, to be semi-permanentlyclosed until resetting is necessary to facilitate reinstallation such asduring engine service. Other objects and advantages of the inventionwill be apparent from the following description when considered inconnection with the accompanying drawings.

The invention in essence provides a hydraulic lash adjuster assembly foran internal combustion engine having a lash adjuster body with a boreformed therein, a plunger assembly, a fluid chamber containing saidplunger assembly; the chamber being equipped to contain therein a supplyof hydraulic fluid. The pressure chamber is formed between the bottom ofsaid first bore and said plunger assembly. The plunger assembly has avalve opening to permit the fluid communication between the fluidchamber and said pressure chamber. A check valve is provided forselectively opening and closing said plunger assembly valve opening. Thecheck valve is arranged such that the check valve opening remains openuntil closed by concurrent engagement of the check valve element and theplunger assembly with the bottom of the bore body in response tomovement of the plunger assembly in an inward direction with respect tothe bore body, and such that the check valve opening then remains closeduntil opened by outside intervention. A biasing means urges the plungerassembly in an outward direction with respect to the bore, thusenlarging the pressure chamber to take up slack in the valve drivetrain. A sealing means engaged with the bore body is activated to movein sealing engagement with the plunger assembly in response to movementof the plunger assembly in an inward direction with respect to the borefor restricting fluid flow from the pressure chamber and to inhibitfurther movement of the plunger assembly in an inward direction. Thelash adjuster being arranged such that the plunger assembly isdisengaged from said sealing means and pressure in said pressure chamberis relieved upon movement of the plunger assembly in an outwarddirection, so that a limit of inward movement can take place each time aload is applied to the plunger assembly before the pressure chamber isagain closed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a prior art hydraulic lash adjuster.

FIG. 2 is an elevational view of the hydraulic lash adjuster of thepresent invention.

FIG. 3A is a cross-sectional view taken along line 3-3 of FIG. 2 showingthe auxiliary check valve in the closed position ready for engineoperation.

FIG. 3B is a cross-sectional view taken along line 3-3 of FIG. 2 showingthe auxiliary check valve in the open position, ready for installationinto an engine valve train.

FIG. 3C is a cross-sectional view taken along line 3-3 of FIG. 2 showingan alternative construction of the auxiliary check valve in the closedposition ready for engine operation.

FIG. 3D is a cross-sectional view taken along line 3-3 of FIG. 2 showingthe alternative construction of the auxiliary check valve illustrated inFIG. 3C, in the open position ready for installation into an enginevalve train.

FIG. 4 is a detail, fragmented, enlarged sectional view of the lowerencircled portion of FIG. 3A to better illustrate the combinationseal-check valve and auxilary check valve.

FIG. 5 is a detail, fragmented, enlarged sectional view of the lowerencircled portion of FIG. 3B to better illustrate the combinationseal-check valve and auxiliary check valve.

FIG. 6 is a perspective view of the auxiliary check valve pin.

FIG. 7 is a perspective view of an alternative construction auxiliarycheck valve pin.

DETAILED DESCRIPTION OF THE INVENTION

This present invention provides the means to facilitate hydraulic lashadjuster installation by providing an auxiliary check valve whichremains open until the lash adjuster plunger has been moved to the limitof its travel. By this means the hydraulic lash adjuster relativelyeasily assumes its proper installed length. A final step in hydrauliclash adjuster installation is the rotation of the camshaft through onefull revolution. During the rotation the valve closing force of eachengine valve spring is in turn transmitted to each hydraulic lashadjuster. This force is sufficient to overcome the opposing force of theplunger return spring and allow the hydraulic lash adjuster to shortento the limit of its available travel.

As the hydraulic lash adjuster is shortened in length, the plungerassembly displaces fluid through the auxiliary check valve from the highpressure chamber to the reservoir chamber. Viscous drag forces acting onthe check valve pin element of the auxiliary check valve areinsufficient to move it since it is held in place within the check valvebody, for example, by means of an interference fit or a spring. As thehydraulic lash adjuster continues to shorten in length, the end of thecheck valve pin extending from the check valve body contacts the lashadjuster body and stops such that the check valve body element of theplunger assembly continues to move until the tapered surfaces of thecheck valve pin and check valve body are mated, halting the flow offluid through the auxiliary check valve and halting as well the movementof the plunger assembly. As the camshaft continues to rotate, theplunger return spring extends the plunger assembly, and as it does so,the combination seal-check valve opens and fluid is drawn from thereservoir chamber to the high pressure chamber until the hydraulic lashadjuster installed length is achieved.

Throughout this and subsequent valve events, the auxiliary check valveremains closed due to the action of a self-locking taper between thecheck valve pin and the check valve body and/or the hydraulic pressuresustained in the high pressure chamber. The auxiliary check valve isable to be reset to the open position, for example during engine valvetrain service, by depressing the check valve pin through the rocker armlubrication port of the ball plunger while holding the ball plungerfixed.

As shown in FIG. 1, a prior art hydraulic lash adjuster 1 is illustratedcomprising a body 3, a plunger assembly 5 defined by a ball plungerelement 7 and a leakdown plunger element 9 which are received within thebody 3 in close fitting relationship and which define a reservoirchamber 11 between them. The bottom of the leakdown plunger element 9forms, in cooperation with the end of a reduced diameter portion 13 ofthe body bore, a high pressure chamber 15. A separate check valve 17 isprovided in the end of a passage 19 which connects the reservoir chamber11 and the high pressure chamber 15. The check valve 17, which is shownas a ball, but which can be a flat disk or the like, is retained by acheck valve retainer 19 which is in interference fit with a counter bore21 formed in the leakdown plunger element and which provides a seat forthe plunger return spring 23.

In general in most prevalent prior art designs a compression spring 25acting between the bottom of the check valve retainer 19 and the checkvalve 17 biases the check valve 17 into a normally closed position. Anoil feed hole 27 opens into the body bore and intersects an oil feedgroove 29 which in turn intersects an oil feed hole 31 in the ballplunger element 7 to supply hydraulic fluid to the reservoir chamber 11.An axial port 33 at the top supplies lubricant to a rocker arm (notshown) which engages the semi-spherical end 35 formed at the upper endof the ball plunger element 7. The plunger assembly 5 is retained withinthe body 3 by means of a cap retainer 37.

In the prior art embodiments of the kind illustrated in FIG. 1, theamount of plunger deflection or “leak down” which occurs during anengine valve event is controlled by the fit between the body bore andthe outside diameter of the leakdown plunger element 9, requiring theclearance between these members to be held very precisely, e.g., to therange of about 5.1-5.8 μm (0.000200-0.000230 in.), which can only beachieved by machining the individual parts to extremely close tolerancesand selectively pairing the leakdown plunger elements and the bodies toobtain the desired clearance. This is an extremely demandingrequirement; a requirement alleviated by the present invention.

Referring to FIG. 3A, a cross-sectional view of the hydraulic lashadjuster 41 configured in accordance with a preferred embodiment of theinvention is shown, comprising a body 43 and a plunger assembly 45slideably fitted within the bore of body 43. The plunger assembly 45 isprovided with a cap element 47 and a valve seat element 49 which isreceived within the base of the body 43 with the cap 47 and top of thevalve seal 49 defining a reservoir chamber 51 between the interior ofcap 47 and the top of the valve seat 49. The bottom of the valve seatelement 49 forms, in cooperation with the bottom portion 53 of theinterior of body 43, a high pressure chamber 55.

It is seen in accordance with the invention that a combinationseal-check valve 57 is provided between passageways and componentclearances which connect the reservoir chamber 51 and the high pressurechamber 55. The combination seal-check valve 57 shown comprises a ringwith a locational transition or locational interference fit with theinterior bore of the body 43. The combination seal-check valve 57 isfree to move within the axial space created between the valve seat 49and a ring seal retainer 59 which is in interference fit on the endportion of valve seat 49. The bottom face of the valve seat 49 providesa seat for the plunger return spring 61.

An oil feed hole 63 opens into the body 43 and intersects an oil feedgroove 65 in the cap element 47 which intersects an oil feed hole 67 inthe cap element 47 to supply hydraulic fluid to the reservoir chamber51. An axial port 69 in the top of the semi-spherical top end 71supplies lubricant to a rocker arm (not shown) which engages thesemi-spherical end 71 formed at the top of the cap 47. The plungerassembly 45 is retained within the body 43 by means of a retainer 73.

With reference to FIG. 3A and, in particular, to the enlargedfragmentary depiction of FIG. 4, it is seen that the auxiliary checkvalve is comprised of a valve pin element 75 which is slideably fittedthrough the bore 77 in valve seat 49.

The amount of plunger deflection which occurs during an engine valveevent is controlled not by “leak down” as in prior art hydraulic lashadjusters of the kind illustrated, for example, by FIG. 1, but by theaxial clearance 79 (FIG. 4) between the combination seal-check valve 57and the valve seat 49 as shown in FIGS. 3A and 4. Because thecombination seal-check valve 57 of the invention is interference fittedto the bore of the body 43, when the plunger assembly 45 shown in FIG.3A is depressed relative to the body 43 during the initial portion ofthe engine valve event, the combination seal-check valve 57 remainsstationary until the plunger assembly has moved through a distance equalto the axial clearance 79.

It is to be noted that, as the plunger assembly 45 is depressed, fluidwithin the high pressure chamber 55 is displaced to the reservoirchamber 51 by first flowing through a multiplicity of openings 81provided in the ring seal retainer 59, through the radial clearance 83and axial clearance 79, then through the radial clearance 85, andfinally, respectively through the multiplicity of connecting valve seatradial and axial passages 87 as shown more clearly in FIG. 4. When fluidpassage through the axial clearance 79 is interrupted by the abutment ofthe combination seal-check valve 57 against the bottom surface 89 (FIG.4) of the valve seat 49, the pathway for fluid flow between the highpressure chamber 55 and the reservoir chamber 51 is closed as shown inFIG. 5 and further plunger deflection is resisted by the resultinghydraulic pressure forces within the high pressure chamber 55.

The hydraulic pressure forces act on the combination seal-check valve 57to enforce respectively axial and radial seals where its surfaces abutthe valve seat 49 and the bore of the body 43 as shown in FIG. 5. At theconclusion of the valve event, the plunger return spring 61 extends theplunger assembly 45 relative to the body 43 to compensate for any lashin the engine valve train (not shown) and as it does so, the axialclearance 79 is restored as shown in FIG. 4 and fluid is transferredfrom the reservoir chamber 51 to the high pressure chamber 55 in themanner previously described.

Those skilled in the art of hydraulic lash adjuster design recognizethat prior art hydraulic lash adjusters incorporating a combinationseal-check valve present difficulties when the adjuster is beinginstalled in an engine valve train because the installed length of thehydraulic lash adjuster within the valve train requires that the plungerassembly 45 be depressed into the body 43 through a distance greaterthan the axial clearance 79. However, as seen by reference to FIG. 3Band FIG. 5, and for the reasons which follow the auxiliary check valveof the present invention resolves this prior art difficulty by the novelarrangement provided.

Referring in particular to FIG. 3B and FIG. 5 it is seen that thehydraulic lash adjuster of the invention comprises a valve pin 75 thatis positioned relative to the valve seat 49 by utilizing an interferencefit between the mating cylindrical surfaces of valve pin 75 and the bore77 (FIG. 5) of valve seat 49. It will be apparent that an alternativeembodiment (not shown) may utilize alternatives, such as a conventionalspring or a frangible element to position the valve pin 75 relative tothe valve seat 49. With the valve pin 75 positioned as shown in FIG. 5,there exists a radial clearance 91 (FIG. 5) between mating taperedsurfaces 93 and 95 respectively of the valve seat 49 and valve pin 75.

As the engine valve train (not shown) is initially rotated to installthe hydraulic lash adjuster 41, depressing the plunger assembly 45 intothe body 43, after the combination seal-check valve has been closed asshown in FIG. 5 by the mechanism previously described, fluid continuesto be displaced from the high pressure chamber 55 to the reservoirchamber 51 through the clearance 91 and through one or more passageways97 formed in the valve pin 75 shown in FIG. 6 or alternatively through ahelical passageway arrangement 103 formed in the valve pin 75 shown inFIG. 7. As the plunger assembly 45 is further deflected, the end bottomportion 99 of the valve pin 75 contacts the interior bottom 101 of thebody 43 and ceases movement. In this position, the valve seat 49 thenslides down over the end portion 95 of valve pin 75, and as it does sodiminishes the clearance 91 to zero, thereby closing the valve to fluidflow and halting further deflection of the plunger assembly.

At the conclusion of the valve event, the plunger return spring 61extends the plunger assembly 45 relative to the body 43 to compensatefor any lash in the engine valve train (not shown) and as it does so,the axial clearance 79 is restored and fluid is transferred from thereservoir chamber 51 to the high pressure chamber 55 in the mannerpreviously described and is position ready as shown in FIG. 3B forengine operation. In a preferred embodiment the mating lower portion 95of valve pin 75 (FIG. 6) and valve seat 49 surfaces comprise aself-locking taper which semi-permanently maintains the valve in theclosed position as shown in FIG. 4. The bottom end portion 99 of thevalve pin 75 which extends below the plunger assembly 45 limits plungertravel in the bore at the bottom 101 (FIG. 5) of the body 43 of thehydraulic lash adjuster assembly. The valve pin 75 may be reset as shownin FIG. 5, for example during engine valve train service, by depressingthe pin 75 relative to the plunger assembly 45 through the port 69.

FIGS. 3C and 3D illustrate an alternate auxiliary check valve whereinthe auxiliary check valve mechanism comprises a spherical configuration105 positioned on the bottom of the body 43 and a suitably configuredopening 77 in the bottom of the

Various alterations and modifications will become apparent to thoseskilled in the art from a reading of the detailed disclosure presentedherein and it is intended that such apparent alterations andmodifications from the disclosure herein provided are encompassed withinthe contemplations of the invention to the extent that such are withinthe scope of the appended claims.

1. A hydraulic lash adjuster assembly for an internal combustion engine,the lash adjuster comprising: a) a lash adjuster body having a body boreformed therein; b) a plunger assembly that includes a reservoir chamberequipped to contain therein a supply of hydraulic fluid positionedwithin said body bore; c) a fluid pressure chamber formed between thebottom of said bore and the bottom of said plunger assembly; d) a valveopening in said plunger assembly to permit fluid communication betweensaid reservoir chamber and said pressure chamber; e) a plunger checkvalve for selectively opening and closing said check valve arranged suchthat the check valve opening remains open until closed by concurrentengagement of the check valve element and the plunger assembly with thebottom of the body bore in response to a linear movement of the plungerassembly thereby retaining the check valve opening in a closed positionuntil opened by outside intervention; f) a biasing means for urging theplunger assembly in a direction that increases the volume of thepressure chamber to take up slack of a valve drive train; g) a sealingmeans engaging the plunger assembly in response to movement of theplunger for restricting fluid flow from the pressure chamber and toinhibit further movement of the plunger assembly; and h) said lashadjuster being arranged such that the plunger assembly is disengagedfrom said sealing means and pressure in said pressure chamber isrelieved upon movement of the plunger assembly as the volume of thepressure chamber increases so as to limit inward movement of the plungerassembly when a load is applied to the plunger assembly and before thepressure chamber is again closed.
 2. The lash adjuster of claim 1wherein the fluid chamber contains a supply of hydraulic fluid.
 3. Thehydraulic lash adjuster of claim 1 where said valve opening in saidplunger assembly comprises a cylindrical coaxial portion and where saidplunger check valve comprises a complementary cylindrical coaxialportion.
 4. The hydraulic lash adjuster of claim 1 wherein said valveopening in said plunger assembly comprises a cylindrical coaxial taperedportion and where said check valve element comprises a sphericalconfiguration coupled with a mating sealable complemental opening. 5.The hydraulic lash adjuster of claim 3 wherein the check valve elementis provided with at least one groove providing fluid communicationbetween said fluid chamber and said pressure chamber such that when saidcheck valve is open, said groove communicates with fluid between saidreservoir chamber and said pressure chamber.
 6. The hydraulic lashadjuster of claim 3 where said groove is longitudinal.
 7. The hydrauliclash adjuster of claim 3 where said groove is helical.
 8. In a hydrauliclash adjuster system for an internal combustion engine, comprising anouter cylindrical body, a plunger assembly slideably positioned withinsaid body and a valve pin movably positioned within said plungerassembly, the improvement comprising: a) a moveable plunger equippedwith an auxiliary check valve in combination with said lash adjuster; b)said check valve devised to be maintained in an open position until theplunger has been moved to a level of its movement range; c) saidcombination upon installation in association with an engine valve withvalve spring and with rotatable camshaft enables the check valve to bemaintained in a closed position by means of a locking contactingengagement by a self-locking auxiliary check valve.